The present invention relates generally to optical network and, more specifically, to maintaining optical networking protocols between optical network connections.
Optical networks generally include a large number of nodes, and often connect to a number of optical networks which may be maintained by a number of different entities. Data flow from and to nodes may vary, and at times any two nodes may communicate on an irregular basis.
Often communications between nodes are subject to particular demands, particularly quality of service demands. These demands may, for example, relate to data rates, data error rates, and other factors. To fulfill these demands connections are made, or unmade, between potentially a large number of nodes to provide reliable delivery of protocols or rate independent services between any two network nodes.
Preferably, light containing data would enter a network at point A and would emerge at point B error-free and without apparent modification, regardless of the number of intermediate nodes or the entities controlling the intermediate nodes. A client utilizing such a connection would be able to transmit at any frequency, with any protocol, and without knowledge of the topology of the optical connection or it's protection scheme. Such an optical network would provide a very valuable feature set by adding manageability, reliability, and connection flexibility to a wavelength.
A rate and protocol independent network would be attractive because such a network provides a transport layer for any type of client that an operator wishes to use. Also, such an optical network would provide connections that are protocol and rate independent allowing any type of client to pass through the network in a transparent manner. Unfortunately the same characteristics that would make a transparent network attractive also complicate realization of the network. Without knowledge of the protocol and the bit-rate being transmitted through the network it is difficult to provide manageability, reliability, and connection flexibility. Without accessing the protocol it is difficult to provide Quality of Service (QOS) guarantees that customers often demand.
Synchronous optical network (SONET) and synchronous data hierarchy (SDH) are standards for optical telecommunication that are increasingly popular and pervasive. However, SONET/SDH, as an optical networking protocol, has an inherent lack of transparency in it's protocol stack. Specifically, SONET/SDH generally does not allow two carriers to mesh their networks without interrupting the management structure of each other. The rigid Section, Line, and Path Termination architecture of SONET/SDH protocols assumes that the end to end link is managed entirely by one carrier, which may not be the case.
As such, the SONET/SDH protocol was not designed to support nested domains and allow carriers to mesh their networks together. Conventionally, the unit of handoff is DS-1 or DS-3, however, neither allows one carrier's management data to tunnel through another's network. As such, SONET/SDH management information contained in the SONET/SDH overhead that may be replaced when a signal leaves one carriers domain and crosses into another would cause difficulties. This management information includes bytes for bit error rate (B1/2/3), section and path trace (J0 and J1), data communication (D1-D12), orderwire and perhaps proprietary bytes. From the original carrier's perspective, the other carrier providing the nested domain has substituted their own overhead information in place of the original bytes. The nested domain is opaque to the bandwidth customers SONET/SDH OAM&P information.